It all comes down to smooth motion and how the brain interprets height
When we ride in a hot air balloon, our brain does not interpret height the same way it does in situations like standing on a cliff or looking down from a tall building. This is mainly because the balloon moves extremely smoothly and steadily, without sudden vibrations or accelerations
Vertigo typically occurs when there is a mismatch between what the eyes see and what the vestibular system (the inner ear balance system) senses. In a balloon, everything moves at the same pace, and there are no rapid motion cues, so the brain does not register immediate danger. Additionally, the basket creates a sense of security, and the distance to the ground is perceived more abstractly, like viewing a distant landscape. All of this makes the experience calm and unlikely to trigger vertigo.
